Volume pedal - make it better?

[DWBH]

So I bought a cheap Proel volume pedal. However, it sucks my tone. It cuts my high end, and decreases the volume slightly.
It's a simple, passive volume pedal, that uses a 20k pot.
I've thought of soldering a cap and a cap in parallel with the input and output lugs of the pot, but I'm not sure what values should I use.
Is the 20k pot adequate, or should I use a 250k pot or something?

Finally, are there any active volume pedal circuits? I've seen that Craig Anderton design, but most people say it's very noisy. Is there any 'worthy' circuit out there?

[earthtonesaudio]

I bet you'd see a big improvement by adding a buffer before and after the volume pot.

[Andi]

Aye - either buffer before (after wouldn't hurt) or a higher value pot.

[MarcoMike]

yes, 20k is a very low value... maybe suitable for active instruments, but the ultimate tone sucker for passive guitar! maybe second to a 10uF cap to ground... 

I would go for something like a few dB booster, like the tillman preamp, with a trim wired somehow to set the max vol with peadal in toe position.